Here is the full list of all 32 Another Crab's Treasure achievements.
Get your shell back.
Defeated Firth.
Try on every shell in the game.
Fully upgrade Kril's fork.
Find a certain hero's helmet.
Defeated the Consortium.
Learn all adaptations.
Defeated the Curdled Carbonara Connoisseur.
Defeated Praya Dubia.
Defeated Camtscha.
Defeated Camtscha (For real.)
Unlock all skills on the Path of The Predator.
Defeated Inkerton.
Purchase some insurance.
Defeated Petroch.
Defeated Roland.
Unlock all skills on the Path of The Hermit.
Unlock all skills on the Path of The True Crab.
Defeated Voltai.
Defeated Topoda.
Defeated Heikea.
Defeated the Diseased Lichenthrope.
Defeated the Ceviche Sisters.
Defeated the Scuttling Sludge Steamroller.
Defeated Pagurus.
Shoot a crab with a gun.
Start the treasure hunt.
Defeated Magista.
Defeated a miniboss.
Fall off a cliff.
Defeated Nephro.
Defeated the Royal Shellsplitter.